Printed wiring board-use copper foil and copper clad laminated sheet using the printed wiring board-use copper foil

ABSTRACT

The object is to provide a copper foil excellent in the property of selective etching between a resistor layer and a copper layer required in production of a printed-wiring board, and also excellent in UL heat resistance. For this purpose, a copper foil for printed-wiring board comprising a nodular treatment side on one side, wherein a nickel-zinc alloy layer is formed on the nodular treatment side is used for applications of printed-wiring boards. At the same time, a production method suitable for production of the copper foil is provided.

TECHNICAL FIELD

[0001] The present invention relates to a copper foil for printed-wiringboard and a method of producing the same, and a copper-clad laminateusing the copper foil for printed-wiring board.

BACKGROUND ART

[0002] For copper foils that have been conventionally used, a variouskinds of copper foils are introduced to the market, and which copperfoil should be used has been determined depending on the uses ofprinted-wiring boards. They include, for example, copper foilscomprising nickel layers for forming resistors, heat-resisting copperfoils to be used for sites that are exothermically affected in a directmanner by electronic equipment, and copper foils having excellentchemical resistance that are advantageously used for formation of finepitch circuits.

[0003] In the trend in recent years toward miniaturization of electricequipment, miniaturization is also required for the printed-wiring boardto be contained therein, and the formed copper foil circuit is furtherreduced in width. Furthermore, as computers operate faster, theprocessing speed is also enhanced, and clock frequencies arecontinuously increasing. Thus, for keeping up with improvement inperformance of computer apparatuses, and achieving furtherminiaturization, provision of fine pitch circuits having increasedwiring densities becomes essential.

[0004] As the wiring density of the printed-wiring board is increasedand components implemented therein are further integrated, the amount ofheat generation is increased, thus causing a problem. For example, thestrength of bonding between the copper foil forming the circuit of theprinted-wiring board and a substrate is reduced with time, and in someextreme cases, the copper foil circuit may be peeled off spontaneouslyfrom the base material. Therefore, current materials for printed-wiringboards are subjected to a variety of treatments to prevent problemsbefore they happen.

[0005] The printed-wiring board can be considered as a composite productcomposed of a metal and a resin material, and thus improvement of itsheat resistance will be influenced by a variety of factors such as thecomposition of the resin material and the type of surface treatment ofthe cupper foil. As copper foils having excellent heat resistance forprinted-wiring boards, those having thick zinc layers or brass layersformed on nodular treatment sides thereof have been widely known. Thatis, the heat resistance with respect to the printed-wiring boardgenerally refers to that of the product conforming to UL Standard. Thethick zinc layer or brass layer provided on the nodular treatment sideof the copper foil for ensuring conformation to UL Standard exhibitsexcellent performance to secure heat resistance.

[0006] On the other hand, in formation of small fine pitch circuits, theprinted-wiring board comprising a 50-μm pitch signal transmissioncircuit with its circuit width of 25 μm and its inter-circuit gap of 25μm has also commonly produced. Thin copper foils have been used inproduction of printed-wiring boards comprising such fine circuitsbecause a satisfactory etching property is required when the copper foilis etched to form a circuit. Also, the additive method has been widelyused in which an outer-layer copper foil is once completely etched away,and thereafter the copper foil circuit is formed by the plating methodor the like.

[0007] However, for processing fine via holes and the like, laserdrilling processing has been used in recent years, thus making itdifficult to process the via hole with the copper foil bonded thereto,and therefore the conformal mask method in which the outer-layer copperfoil is partially etched away to carry out laser drilling processing,the method in which the outer-layer copper foil for improving accuracyof position for drilling process is wholly etched away, and so on areemployed. Then, after laser drilling processing is carried out, a copperlayer is formed through the panel plating method and patterned to form acircuit in the site in which the copper foil has been etched away, or acopper foil circuit is directly formed by the additive method.

[0008] The problem arising in such methods is that after the copper foilis once removed, a surface treatment layer that would exist if theoriginal copper foil were used does not exist in the interface betweenthe circuit formed by the panel plating method or the additive methodand the substrate. That is, absence of the surface treatment layer meansthat in the circuit portion is provided no means for purposely improvingits chemical resistance and heat resistance.

[0009] Therefore, in particular, the heat resistance property of thatcircuit portion is significantly reduced compared to the case where anormal copper foil having improved heat resistance is used, andmaterials and methods preventing such a problem from arising have beendesired.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIGS. 1 and 8 are schematic sectional views of copper foils forprinted-wiring boards according to the present invention.

[0011]FIGS. 2. to 7 are each presented as a flow chart showing a processfor producing a printed-wiring board that is used in the followingdescription.

SUMMARY OF THE INVENTION

[0012] Then, as a result of conducting vigorous studies, the inventorsof the present invention have considered that the above describedproblem can be solved by providing a copper foil comprising anickel-zinc alloy layer on the nodular treatment side. The presentinvention will be described below.

[0013] In claims is described a copper foil for printed-wiring boardcomprising on one side a nodular treatment side to be bonded to asubstrate, characterized in that a nickel-zinc alloy layer is providedon the nodular treatment side. FIG. 1 is a schematic sectional viewshowing this copper foil for printed-wiring board.

[0014] Here, the description of “a nickel-zinc alloy layer is providedon the nodular treatment side” implies that nodular treatment is appliedto one side of a copper foil 2, and then a nickel-zinc alloy layer 5 isformed on the surface obtained after the nodular treatment. The term“nodular treatment” used herein means a treatment for providingirregularities formed on the bonding side of the copper foil when thecopper foil and the substrate are bonded together for producing a copperclad laminate. Formation of the irregularities is generally carried outby depositing copper microparticles 4 on the surface by electrolysis.The method can also be employed in which the one side of the copper foillayer 2 is etched, thereby providing only one side of the copper foillayer 2 with a matte face.

[0015] Then, the “nickel-zinc alloy layer” is formed on the sidesubjected to nodular treatment, whereby the selective etching propertyis ensured, and the heat resistance specified in UL 796 Standard(hereinafter referred to as “UL heat resistance” is ensured at the sametime. The term “selective etching property” described in thisspecification is used to imply that only the copper component isdissolved, and nickel or a nickel-zinc alloy is not dissolved. Thisselective etching property functions as a very useful property in themethod of printed-wiring boards described later.

[0016] Up to this time, the concept of using nickel or a nickel-zincalloy for surface treatment of the copper foil has been adopted forimproving chemical resistance mainly in the sense that no damage iscaused by chemical solutions used in the process of production of theprinted-wiring board. As a result of conducting vigorous studies, theinventors of this invention have envisioned a certain method ofproducing printer-wiring plates, and considered that in the method, aprotective layer for ensuring heat resistance could be left below theformed circuit even if the panel plating method or additive method isused. Thus, explanation will be presented showing the method of usingthis copper foil for printed-wiring board according to claim 1.

[0017]FIG. 2A shows a so called four-layer plate 11 in which a copperfoil for printed-wiring board. 1 according to this invention is bondedto the both outer faces of a core substrate 8 comprising an innercircuit 7, and shows therebelow a flow for subjecting this substrate tolaser drilling processing to form a via hole 14 so as to produce aprinted-wiring board 18 having a fine pitch pattern.

[0018] For the four-layer plate 11 shown in FIG. 2A, copper foil layers2 on the both outer faces and the copper component of coppermicroparticles 4 are first etched away for carrying out laser drillingprocessing. At the time of etching them away, if an acid etchant such asa ferric chloride solution and copper sulfate based solution being anormal etchant for etching copper, the nickel-zinc alloy layer 5 as asurface treatment layer is also dissolved away along with the coppercomponent, leading to a result similar to that when a conventionalnormal copper foil is used. However, if so called an alkali etchant orsulfuric acid-hydrogen peroxide based solution is used as an etchant foretching copper, the nickel or nickel-zinc alloy layer 5 remains withoutbeing dissolved, and the nickel or nickel-zinc alloy 5 appears on theboth outer faces as shown in FIG. 3B.

[0019] The surface treatment applied to the matte side 3 of the copperfoil layer 2 has never unnecessarily increased the amount of corrosionpreventing elements except for the case where surface treatment iscarried out using zinc or a zinc alloy for ensuring heat resistance.Therefore, the amount of deposited nickel or nickel alloy layer 5 issmall, and the nickel or nickel alloy layer 5 is not found to remain onthe surface of the substrate, and it can be said that all the layer isremoved including the surface treatment layer. In the case of thepresent invention, however, the nickel or nickel alloy layer 5 should bemade to remain in a recognizable way.

[0020] Then, in the case of the copper foil for printed-wiring board 1,its composition is also important. As described in claim 2, anickel-zinc alloy having 70 to 88 wt % of nickel and the balance of zincis preferably used for the nickel-zinc alloy. If the content of nickelin the nickel-zinc alloy is smaller than 70 wt %, the content of zincincreases, and it becomes impossible to carry out selective etchingdescribed above although UL heat resistance is more advantageouslyensured. On the other hand, if the content of nickel in the nickel-zincalloy exceeds 88 wt %, then the content of zinc decreases. In this case,even though the selective etching property is quite excellent, the ULheat resistance does not satisfy the value specified in the Standard.

[0021] Also, the thickness of the nickel-zinc alloy is very important.In claim 3 is described the copper foil for printed-wiring boardaccording to claim 1 or 2, characterized in that the thickness of thenickel-zinc alloy is 0.07 g to 45 g per square meter of nodulartreatment side of the copper foil. The thickness should be normallyexpressed using units for length such as μm, but the nodular treatmentside of the copper foil has irregularities as apparent from FIG. 1, andcopper microparticles are deposited thereon for obtaining an anchoreffect when it is bonded to the substrate, thus making it difficult touse a unit for length. Thus, the deposited amount per square meter isused as a unit corresponding to the thickness of the nickel-zinc alloylayer.

[0022] The specific surface area of the nodular treatment side of ageneral copper foil varies depending on the thickness of the copperfoil. Therefore, if the thickness of the nickel-zinc alloy layer issmaller than 0.7 g per square meter of nodular treatment side of thecopper foil, stability is reduced in the sense that the nodulartreatment side of the normally conceivable whole thickness of copperfoil is covered uniformly and without irregularity. If the thickness ofthe nickel-zinc alloy layer exceeds 45 g per square meter, theirregularities for obtaining the anchor effect of the nodular treatmentside of the normally conceivable whole thickness of copper foil may beeliminated or changed into a flat shape. Thus, the thickness derived asoptimum conditions allowing the nickel-zinc alloy layer to be formed asa surface treatment layer for the nodular treatment side of the normallyconceivable whole thickness of copper foil is 0.7 g to 45 g per squaremeter of nodular treatment side of the copper foil.

[0023] Then, a laser beam is applied to a predetermined location tocarry out laser drilling processing. It is known that drillingprocessing with the use of a carbon dioxide gas is difficult if thecopper foil exists. On the other hand, the inventors of this inventionhave recommended nickel as a material enabling drilling processing to becarried out quite easily. A theory demonstrating that the nickel layeror nickel alloy layer has excellent laser drilling processability hasnot yet been established. In the process of continuous studies, however,the inventors of this invention have come to believe that the laserdrilling processability is improved based on the following principle.

[0024] When a metal is subjected to drilling processing by a laser, aprocess in which the metal is continuously vaporized in an amountcorresponding to predetermined thickness of metal layer must bereproduced. In other words, during application of a laser, thetemperature of at least the site to which the laser is applied must behigher than the boiling point of nickel or the nickel alloy. Copper thatcan hardly be subjected to laser drilling processing is an elementclassified as a precious metal belonging to the IB group of the periodiclaw, and has as its properties a melting point of 1083° C., a boilingpoint of 2582° C., and a melting enthalpy (heat of melting) of 13.3kJ/mol under the condition of 1.01×10⁵ Pa.

[0025] On the other hand, nickel is classified as an element belongingto the VIII group of the periodic law, and has as its properties amelting point of 1455° C., a boiling point of 2731° C., and a meltingenthalpy (heat of melting) of 17.6 kJ/mol under the condition of1.01×10⁵ Pa. The boiling point of nickel is about 150 to 160° C. higherthan the boiling point of copper. So far as these properties areconcerned, nickel and the nickel alloy are more stable than copper withrespect to heat. Therefore, drilling processing using a laser beam iscarried out by providing high energy to the site exposed to the laserbeam, thereby sharply increasing the temperature of the site to causethe material of the site to be melted and vaporized, and therefore itcannot be thought that the assumption that nickel and the nickel alloyare more easily drilled than copper holds.

[0026] Here, the thermal conductivity of copper is compared to that ofnickel. Copper has thermal conductivity of 354 W.m⁻¹.K⁻¹ at 700° C., andis a good heat conductor. On the other hand, nickel has thermalconductivity of 71 W.m⁻¹.K⁻¹ at 700° C., which is approximately ⅕ of thethermal conductivity of copper, and it can be understood that nickel hasvery low heat conductivity compared to copper. In view of this fact, itcan be considered that copper being a good heat conductor quicklydiffuses heat given by the laser beam, thus making it difficult forconcentrated heat to remain in one site. Then, it is also known thatnickel has high absorptance for laser beams compared to copper. Fromthese facts, it can be considered that because copper has lowabsorptance for laser beams, and heat energy supplied to the copper foilsite exposed to the laser beam decreases causing heat given to thecopper foil layer to be defused quickly, the temperature of the site inthe copper foil exposed to laser beam hardly rises above the boilingpoint to reduce laser drilling processability.

[0027] Nickel conducts heat at a rate about ⅕ of the heat conductivityof copper. Also, because of its high absorptance for laser beams, nickelhas a high efficiency of conversion to heat energy compared to copper.Therefore, it can be considered that heat energy is easily concentratedon the site exposed to the laser beam, and the speed at which heatenergy is supplied by the laser beam than the speed at which heat isdiffused, and the site exposed to the laser beam easily reaches themelting point of nickel, thus improving laser drilling processability.If the aforementioned absorptance for laser beams is compared for copperand nickel having same levels of surface roughness, the reflectivity ofnickel is apparently smaller than that of copper by about 1% to 2%, andthus the absorptance for laser beams by nickel is higher.

[0028] As a result, it can be considered that nickel undergoes quicktemperature rising by application of a laser beam, and is easily meltedand vaporized in spite of the fact that its melting point is higher thanthat of copper. Therefore, a similar result can be obtained if anickel-zinc alloy having the composition mentioned in the presentinvention, existence of the alloy layer on the outer face of thesubstrate does not hinder at all laser drilling processability. FIG. 3Cshows a situation in which laser drilling processing is carried out toform the via hole 14, and desmear treatment is carried out.

[0029] Here, what is brought about as another effect is that a solutioncapable of dissolving the resin of the insulation resin layer is usedfor the solution of desmear treatment, and therefore it vanishes evenirregularities on the outer face of the substrate, thus reducing theadhesion to the substrate of a copper layer subsequently formed by theplating method or the like. If using copper foil for printed-wiringboard according to present invention, however, irregularities on theouter face of the substrate remain intact so that the anchor effect canbe obtained because the nickel-zinc alloy layer exists on the outermostlayer, thus making it possible to improve adhesion between the platedlayer and the substrate.

[0030] From this point, a copper plated layer is formed on the entiresurface of the substrate including the inner wall of the via hole 14 inthe case of the plating method, as shown in FIG. 4D. Then, as shown inFIG. 4E, an etching resist layer 16 is formed on the surface of thecopper plated layer 15, and as shown in FIG. 5F, a circuit pattern isdeveloped by light exposure on the etching resist layer 16, and a acidetchant for copper is used to carry out circuit etching, and the etchingresist is peeled off to obtain the printed-wiring board 18 as shown inFIG. 15G. If the above described production method is adopted, thenickel-zinc layer 5 exists in the interface between the circuit on theouter face and the substrate, thus making it possible to obtain a platehaving excellent UL heat resistance.

[0031] When the semiadditive method is adopted, on the other hand, thefollowing flow is applied. For the plate shown in FIG. 3C that has beensubjected to laser drilling processing to form the shape of the via hole14 and has undergone desmear treatment, the etching resist layer 16 isformed on the surface of the exposed nickel-zinc layer 5 as shown inFIG. 6D without forming a plated layer, a circuit pattern is developedby light exposure on the etching resist layer 16 as shown in FIG. 6E,the nickel-zinc layer 5 is etched into a circuit shape using an etchant,and the etching resist is peeled off to provide a situation shown inFIG. 7F. Then, the copper plated layer 15 is formed on the nickel-zinclayer 5 shaped like a circuit and on the inner wall of the via hole 14,whereby the printed-wiring board 18 as shown in FIG. 7G can be obtained.Adoption of this production method makes it possible to obtain a platehaving excellent UL heat resistance in which the nickel-zinc layer 5exists in the interface between the circuit and the substrate in a sameway as FIG. 5G.

[0032] If assuming the uses described above, a copper foil in which asurface treatment layer capable of undergoing selective etching withcopper is provided, and the UL heat resistance of the surface treatmentlayer is excellent is required. Therefore, a copper foil having thoseproperties together is the copper foil for printed-wiring board definedin claims. Furthermore, all the copper foils can be formed into copperclad laminates, and processed into printed-wiring boards by normaletching process, and in this case, excellent UL heat resistance is alsoensured.

[0033] In addition, a copper foil having a similar effect is the copperfoil for printed-wiring board comprising on one side a nodular treatmentside to be bonded to a substrate according to another claim,characterized in that a nickel layer is provided on the nodulartreatment side, and a zinc layer or a zinc alloy layer is provided onthe nickel layer. FIG. 8 shows a schematic sectional view of this copperfoil. As apparent from FIG. 8, the nickel layer 5 is provided on thenodular treatment side, and a zinc layer or a zinc alloy layer 19typically of brass or the like is provided on the nickel layer 5 as asurface treatment layer. The nickel layer 5 serves to protect the zinclayer or zinc alloy layer 19 typically of brass provided for the purposeof ensuring UL heat resistance when the copper component of the copperfoil is subjected to selective etching with respect to the four-layerplate 11 shown in FIG. 2A.

[0034] Therefore, uses similar to those of the copper foils describedabove can be adopted for this copper foil for printed-wiring board, andthe printed-wiring board obtained by a production method similar tothose described above allows a fine pitch circuit to be easily formed,and enables a circuit having UL heat resistance to be provided.

[0035] For this copper foil for printed-wiring board, however, thenickel layer and the surface treatment layer dependently of each other,and therefore unless the total thickness of the nickel layer and surfacetreatment layer formed on the nodular treatment side of the copper foilis considered, irregularities on the nodular treatment side arevanished, and the anchor effect of the plated layer can no longer beobtained when the copper foil is processed into the printed-wiringboard. Thus, claim 5 provides a copper foil for printed-wiring board inwhich the weight thickness (X) of the nickel layer is in the range offrom 0.7 g/m² to 45 g/m², the weight thickness (Y) of the zinc layer isin the range of from 0.01 g/m² to 2 g/m², and the reduced thickness (T)calculated from Equation 1 is smaller than or equal to 5 μm, and claim 6provides a copper foil for printed-wiring board in which the weightthickness (X) of the nickel layer is in the range of from 0.7 g/m² to 45g/m², the weight thickness (Z) of the zinc alloy layer containing nkinds of alloying elements is in the range of from 0.01 g/m² to 2 g/m²,and the reduced thickness (T) calculated in accordance with theprocedure shown in Equation 2 is smaller than or equal to 5 μm, therebyspecifying their appropriate thickness. The nickel layer has a minimumthickness of 0.7 g/m² for achieving a uniform and defect-free thicknessin consideration of the selective etching property. At this time, theminimum necessary thickness of the zinc layer or zinc alloy layerrequired for conforming to the Standard of UL heat resistance is 0.01g/m². Thus, the reason why the expression has been used such that thetotal thickness is “smaller than or equal to 5 μm” is that the lowerlimit of total thickness is spontaneously determined from the minimumnecessary value in the range of weight thickness of nickel, zinc or thezinc alloy.

[0036] Unless the total thickness of the nickel layer and the zinc layeror the zinc alloy layer is considered, irregularities on the nodulartreatment side of the copper foil are vanished, and adhesion of thecopper foil can no longer be ensured when the copper foil is processedinto the copper clad laminate. As described previously, becauseirregularities are provided on the nodular treatment side of the copperfoil, it is difficult to express the thickness using gage thickness ofthe nickel layer and the zinc layer, and thus weight thickness isusually used. Thus, the total thickness of the nickel layer and the zinclayer or the zinc alloy layer is considered using this weight thickness.

[0037] However, the concept of total thickness is different for the caseof combination of the nickel layer and zinc layer in the nodulartreatment side of the copper foil and the case of combination of thenickel layer and zinc alloy layer in the nodular treatment side of thecopper foil.

[0038] First, the thickness in the case of combination of the nickellayer and zinc layer in the nodular treatment side of the copper foil isconsidered in the following manner. In reality, however, it is difficultto calculate correct thickness in a plane surface having smallirregularities, and therefore the thickness is reduced into a value thatwould be determined for a flat surface with experimental empiricalvalues taken into consideration. Here, the Ni layer is formed inthickness of X (g) per square meter, and its reduced thickness equalsX/8.85 (μm) provided that the specific gravity of nickel is 8.85 g/m³.If the Zn layer is formed on the nickel layer in thickness of Y (g) persquare meter, then its thickness equals Y/7.12 (μm). Therefore, thetotal thickness of the Ni layer and zinc layer equals (X/8.85)+(Y/7.12)(μm).

[0039] Next, the thickness in the case of combination of the nickellayer and zinc alloy layer in the nodular treatment side of the copperfoil is considered in the following manner. Here, the zinc alloy isconsidered as an alloy of Zn and n kinds of different metals. It isconsidered that the zinc alloy is deposited in thickness of Z (g) persquare meter. Then, assume that the content of zinc in the zinc alloy isa % by weight, and the contents of constituent elements of n kinds ofdifferent metals (Me₁, Me₂, . . . , Me_(n)) are b₁% by weight, b₂% byweight, . . . , b_(n)% by weight, respectively. That is, the equation ofa+(b₁+b₂+ . . . +b_(n))=100 wt % holds. Then, the specific gravityρ_(sum) of the alloy is given by equation 3. $\begin{matrix}{\rho_{sum} = {\frac{\left\{ {{7.12 \times a} + \left( {{\rho_{Me1} \times b_{1}} + {\rho_{Me2} \times b_{2}} + \ldots + {\rho_{Men} \times b_{n}}} \right)} \right\}}{100}.}} & {{Equation}\quad 3}\end{matrix}$

[0040] Therefore, the reduced thickness of the zinc alloy layer isconsidered as X/ρ_(sum) (μm). From these considerations, the totalthickness of the nickel layer and the zinc alloy layer is calculated as(X/8.85)+(Z/ρ_(sum)) (μm).

[0041] Experience shows if the reduced total thickness described aboveis larger than 5μ, irregularities on the nodular treatment side of thecopper foil are vanished. On the other hand, even if the thickness ofthe nickel layer is larger than 45 g/m², it contributes neither toimprovement of the selective etching property nor to stability ofthickness. In addition, nickel is expensive, and therefore it is desiredthat the amount of nickel to be used is reduced wherever possible. Forthese reasons, the upper limit of weight thickness (X) of the nickellayer is 45 g/m². When the upper limit of thickness of the nickel layeris determined, the upper limit of thickness of the zinc layer or zincalloy layer required for satisfying the conditions of total thicknessdescribed above is inevitably determined.

[0042] The copper foil for printed-wiring board described above exhibitsits properties advantageously particularly in the uses as describedabove, but is also capable of adapting to other uses similar to those ofusual copper foils, and the printed-wiring board obtained from thecopper clad laminate produced using the copper foil for printed-wiringboard has excellent UL heat resistance. Thus, claim 7 provides a copperclad laminate using the copper foil for printed-wiring board accordingto claims 1 to 6, wherein the copper clad laminate includes the conceptsof both rigid type and flexible type, and covers any layer structures ofsingle-sided, double-sided and multilayered structures.

BEST MODE FOR CARRYING OUT THE INVENTION

[0043] The results of producing a copper foil for printed-wiring boardaccording to the present invention, producing a multilayerprinted-wiring board, and measuring UL heat resistance will be describedbelow.

EXAMPLE 1

[0044] In this Example, the steps of producing a printed-wiring boardusing a copper foil for printed-wiring board comprising an alloy layerof nickel and zinc on the matte side of an electrodeposited copper foilwill be described. First, production of the copper foil forprinted-wiring board 1 will be described with reference to the drawings.Here, an electrodeposited copper foil having a cross section shownschematically in FIG. 1 for use in producing a copper foil havingnominal thickness of 18 μm, which had not been subjected to surfacetreatment (hereinafter referred to as “untreated copper foil”) was used.Then, a so called surface treatment apparatus was used to subject thisuntreated copper foil 2 to nodular treatment and surface treatment forforming the nickel-zinc layer.

[0045] In the surface treatment apparatus, copper microparticles 4 arefirst deposited on the surface of the matte side 3 of the untreatedcopper foil 2 under burnt copper plating conditions. For the burntcopper plating conditions for the copper microparticles 4, plating wascarried out under conditions of current density of 30 A/dm² andelectrolysis time of 4 seconds by using an insoluble anode (DSE) for thecounter electrode to make the copper foil itself undergo cathodepolarization, in a copper sulfate solution at a liquid temperature of30° C. with concentrations of copper and sulfuric acid being 12 g/l and180 g/l, respectively.

[0046] Then, the nickel-zinc alloy layer 5 was formed on the surfacewith the copper microparticles 4 provided thereon. For this nickel-zincalloy layer 5, a pyrophosphate based solution was prepared with the useof zinc pyrophosphate (ZnP₂O₇.3H₂O), nickel sulfate (NiSO₄.7H₂O) andpotassium pyrophosphate (K₂P₄O₇) so that the solution had a compositionwith 1.0 g/l of zinc, 10.0 g/l of nickel and 100 g/l of potassiumpyrophosphate, and in the solution at a liquid temperature of 30° C.,the copper foil itself was made to undergo cathode polarization with theuse of a stainless plate for the counter electrode under conditions ofcurrent density of 1 A/dm² and electrolysis time of 300 seconds, therebyproviding an alloy composition with 2.28 g/m² (70.1 wt %) of nickel and0.95 g/cm² (29.9 wt %) of zinc. The weight thickness of the nickel-zincalloy layer 5 was 3.23 g/m². In concurrence with this formation of thenickel-zinc alloy layer 5 on the nodular treatment side 4, 0.10 g/m² ofnickel-zinc layer was formed on the shiny side 6 of the untreated copperfoil 2 as a corrosion prevention layer. In addition, the surface withthe nickel-zinc alloy layer 5 formed thereon was treated with a silanecoupling agent and then dried to produce the copper foil forprinted-wiring board 1 shown in FIG. 1. However, the nickel-zinc alloylayer 5 formed on the surface of the shiny side 6, and the silanecoupling agent treated layer are not shown in the drawings.

[0047] The steps of producing a printed-wiring board using the copperfoil for printed-wiring board obtained in the above described steps willbe described below referring to FIGS. 2 to 5. The copper foil forprinted-wiring board 1 according to the present invention was bonded tothe both outer faces of a core substrate 8 comprising an inner circuit 7with an insulation layer 10 formed wit the use of a prepreg 9 underusual hot press conditions, and thereby a so called four-layer plate 11shown in FIG. 2A was produced.

[0048] Then, for the four-layer plate 11 shown in FIG. 2A, the coppercomponent of the untreated copper foil 2 and the copper microparticles 4on the both outer faces were first etched away for carrying out laserdrilling processing. At the time when the copper component was etchedaway, “A” process solution (manufactured by Meltex Co., Ltd.) being socalled an alkali etchant was used as a etchant for copper, therebyallowing the nickel-zinc alloy layer 5 to be exposed at the both outerfaces as shown in FIG. 3B with the nickel-zinc alloy layer 5 remainingwithout being dissolved.

[0049] Then, a laser beam 12 was applied to a predetermined location tocarry out drilling processing to bore a via hole 14 with a carbondioxide laser 13. For the irradiation conditions of the carbon dioxidelaser 13, the frequency was 2000 Hz, the mask diameter was 5.0 mm, thepulse width was 60 μsec., the pulse energy was 16.0 mJ, the offset was0.8 and the laser beam diameter was 140 μm, so that a process diameterof 110 μm was provided. At this time, even if the nickel-zinc alloylayer 5 existed, drilling processability was not compromised at all, butrather a satisfactory via hole shape could be provided. Thereafter,desmear treatment was carried out to smooth the inner surface of the viahole 14 and remove remainders such as resin remaining on the bottom ofthe via hole 14, thereby providing a situation shown in FIG. 3C.

[0050] In addition, as an effect obtained in a overlapping way, it couldbe ensured that due to a solution for desmear treatment, the resin ofthe insulation layer 10 is prevented from being dissolved, andirregularities on the outer face of the plate are not vanished, becauseof existence of the nickel-zinc alloy layer 5 on the outermost layer.This is effective in the sense that adhesion to the substrate of theplated layer formed in the subsequent step is improved.

[0051] Here, the panel plating method was used to form a copper platedlayer 15 with average thickness of 15 μm on the entire surface of thesubstrate including the inner surface of the via hole 14. For copperplated conditions at this time, a copper sulfate solution was used withconcentrations of sulfuric acid and copper being 150 g/l and 65 g/l,respectively, and with liquid temperature of 45° C., current density of15 A/dm²and electrolysis time of 140 seconds. Then, an etching resistlayer 16 was formed on the surface of the copper plated layer 15 withthe use of a dry film as shown in FIG. 4E, and a circuit pattern wasdeveloped through light exposure on the etching resist layer 16 as shownin FIG. 5F, and an acid etchant for copper was used to carry out circuitetching, and the etching resist layer 16 was peeled to obtain aprinted-wiring board 18 with an outer circuit 17 as shown in FIG. 5G.

[0052] The printed-wiring board 18 obtained as described above was usedto measure the peel strength at the interface between the outer circuit17 and the isolation layer 10. As a result, the dry peel strength was1.89 kgf/cm, and the level of UL heat resistance at rating 130° C.defined in the UL 796 Standard was 0.85 kgf/cm, both well surpassing thevalues (10 days) specifying the UL standard.

EXAMPLE 2

[0053] In this Example, the steps of producing a printed-wiring boardwith the use of a copper foil for printed-wiring board comprising analloy layer of nickel and zinc on the matte side of an electrodepositedcopper foil will be described. First, production of the copper foil forprinted-wiring board 1 will be described with reference to the drawings.Here, an electrodeposited copper foil having a cross section shownschematically in FIG. 1 for use in producing a copper foil havingnominal thickness of 18 μm, which had not been subjected to surfacetreatment (hereinafter referred to as “untreated copper foil”) was used.Then, a so called surface treatment apparatus was used to subject thisuntreated copper foil 2 to nodular treatment and surface treatment forforming the nickel-zinc layer.

[0054] In the surface treatment apparatus, copper microparticles 4 arefirst deposited on the surface of the matte side 3 of the untreatedcopper foil 2 under burnt copper plating conditions, and seal platingwas carried out as level copper plating conditions so as to prevent thecopper microparticles 4 from being dropped off, thereby depositingstably the copper microparticles 4 on the matte side 3 of the untreatedcopper foil 2. For the burnt copper plating conditions for the coppermicroparticles 4, plating was carried out under conditions of currentdensity of 30 A/dm² and electrolysis time of 4 seconds by using aninsoluble anode (DSE) for the counter electrode to make the copper foilitself undergo cathode polarization, in a copper sulfate solution at aliquid temperature of 30° C. with concentrations of copper and sulfuricacid being 12 g/l and 180 g/l, respectively. For the level copperplating conditions for the copper microparticles 4, plating was carriedout under conditions of current density of 15 A/dm² and electrolysistime of 4 seconds with the use of a stainless plate for the counterelectrode to make the copper foil itself undergo cathode polarization,in a copper sulfate solution at a liquid temperature of 30° C. withconcentrations of copper and sulfuric acid being 40 g/l and 180 g/l,respectively.

[0055] Then, the nickel-zinc alloy layer 5 was formed on the surfacewith the copper microparticles 4 provided thereon. For this nickel-zincalloy layer 5, a pyrophosphate based solution was prepared using zincpyrophosphate (ZnP₂O₇.3H₂O), nickel sulfate (NiSO₄.7H₂O) and potassiumpyrophosphate (K₂P₄O₇) so that the solution had a composition with 0.2g/l of zinc, 2.3 g/l of nickel and 100 g/l of potassium pyrophosphate,and in the solution at a liquid temperature of 30° C., the copper foilitself was made to undergo cathode polarization using a stainless platefor the counter electrode under conditions of current density of 2 A/dm²and electrolysis time of 150 seconds, thereby providing an alloycomposition with 0.76 g/m² (76.0 wt %) of nickel and 0.24 g/cm² (24.0 wt%) of zinc. The weight thickness of the nickel-zinc alloy layer at thistime was 1.00 g/m². In concurrence with this formation of thenickel-zinc alloy layer 5 on the matte side 3, 0.10 g/m² of nickel-zinclayer was formed on the shiny side 6 of the untreated copper foil 2 as acorrosion prevention layer. In addition, the surface with thenickel-zinc alloy layer 5 formed thereon was treated with a silanecoupling agent and then dried to produce the copper foil forprinted-wiring board 1 shown in FIG. 1. However, the nickel-zinc alloylayer 5 formed on the surface of the shiny side 6, and the silanecoupling agent treated layer are not shown in the drawings.

[0056] Thereafter, the printed-wiring board 18 was produced through amethod similar to that used in Example 1, comprised of the steps shownin FIGS. 2 to 5. This printed-wiring board 18 was used to measure thepeel strength at the interface between the outer circuit 17 and theisolation layer 10. As a result, the dry peel strength was 1.89 kgf/cm,and the level of UL heat resistance at rating 130° C. defined in the UL796 Standard was 1.15 kgf/cm, both well surpassing the values (10 days)specifying the UL standard.

EXAMPLE 3

[0057] In this Example, the steps of producing a printed-wiring boardusing a copper foil for printed-wiring board comprising two layers,namely nickel and zinc layers on the nodular treatment side of anelectrodeposited copper foil will be described. First, production of thecopper foil for printed-wiring board 1 will be described with referenceto the drawings. Here, an electrodeposited copper foil having a crosssection shown schematically in FIG. 8 for use in producing a copper foilhaving nominal thickness of 18 μm, which had not been subjected tosurface treatment (hereinafter referred to as “untreated copper foil”)was used. Then, a so called surface treatment apparatus was used tosubject this untreated copper foil 2 to nodular treatment and surfacetreatment for forming the nickel and zinc layers.

[0058] In the surface treatment apparatus, copper microparticles 4 arefirst deposited on the surface of the matte side 3 of the untreatedcopper foil 2 under burnt copper plating conditions, and seal platingwas carried out as level copper plating conditions so as to prevent thecopper microparticles 4 from being dropped off, thereby depositingstably the copper microparticles 4 on the matte side 3 of the untreatedcopper foil 2. For the burnt copper plating conditions for the coppermicroparticles 4, plating was carried out under conditions of currentdensity of 30 A/dm² and electrolysis time of 4 seconds by using aninsoluble anode (DSE) for the counter electrode to make the copper foilitself undergo cathode polarization, in a copper sulfate solution at aliquid temperature of 30° C. with concentrations of copper and sulfuricacid being 12 g/l and 180 g/l, respectively. For the level copperplating conditions for the copper microparticles 4, plating was carriedout under conditions of current density of 15 A/dm² and electrolysistime of 4 seconds by using the insoluble anode (DSE) for the counterelectrode to make the copper foil itself undergo cathode polarization,in a copper sulfate solution at a liquid temperature of 30° C. withconcentrations of copper and sulfuric acid being 40 g/l and 180 g/l,respectively.

[0059] Then, a nickel layer 5 was formed on the surface with coppermicroparticles 4 provided thereon. For this nickel layer 5, a nickelsulfate based solution was prepared so that the solution had acomposition with 300 g/l of nickel sulfate (NiSO₄.7H₂O), 50 g/l ofnickel chloride (NiCl₂) and 40 g/l of boric acid (H₃BO₃), and in thesolution at a liquid temperature of 30° C., the copper foil itself wasmade to undergo cathode polaraization with the use of a stainless platefor the counter electrode under conditions of current density of 24A/dm² and electrolysis time of 12.6 seconds, thereby electro-depositing8.24 g/m² of nickel.

[0060] Subsequently, a zinc layer 19 was formed on the surface of thenickel layer 5. With a solution having concentrations of zinc andpotassium pyrophosphate being 6 g/l and 100 g/l, respectively, thecopper foil itself was made to undergo cathode polarization with the useof a stainless plate for the counter electrode in the solution at aliquid temperature of 25° C. under conditions of current density of 6A/dm² and electrolysis time of 2 seconds, thereby electrodepositing 0.20g/m² of zinc.

[0061] The reduced thickness of the nickel layer 5 and the zinc layer 19is 0.96 μm (0.96 +zinc) from Equation 1. In concurrence with thisformation of this zinc layer 19, 0.02 g/m² of zinc layer was formed onthe shiny side 6 of the untreated copper foil 2 as a corrosionprevention layer. In addition, the surface with the zinc layer 5 formedthereon was treated with a silane coupling agent and then dried toproduce the copper foil for printed-wiring board 1 shown in FIG. 8.However, the zinc layer formed on the surface of the shiny side 6, andthe silane coupling agent treated layer are not shown in the drawings.

[0062] Thereafter, the printed-wiring board 18 was produced by a methodsimilar to that used in Example 1, comprised of the steps shown in FIGS.2 to 5. This printed-wiring board 18 was used to measure the peelstrength at the interface between the outer circuit 17 and the isolationlayer 10. As a result, the dry peel strength was 1.89 kgf/cm, and thelevel of UL heat resistance at rating 130° C. defined in the UL 796Standard was 1.15 kgf/cm, both well surpassing the values (10 days)specifying the UL standard.

EXAMPLE 4

[0063] Here, the case where the additive method was adopted for formingthe outer circuit 17 will be described. Thus, the steps shown in FIGS.2A to 3C are similar to those of Example 1. Therefore, in order toprevent redundancy, such steps will not be described here. Also, for thesymbols in the drawings, common symbols will be used wherever possible.The subsequent steps proceeds in accordance with the following flow. Theetching resist layer 16 was formed as shown in FIG. 6D on the surface ofthe exposed nickel-zinc alloy layer 5 of a substrate subjected to laserdrilling processing shown in FIG. 3C to provide a via hole shapetherein, and made to undergo desmear treatment, and a circuit patternwas developed by light exposure on the etching resist layer 16, and anetchant was used to etch the nickel-zinc alloy layer 5 in a circuitshape as shown in FIG. 7F, and the remaining etching resist layer 16 waspeeled off, thereby leaving only the nickel-zinc alloy layer 5 on thesite forming the outer circuit 17.

[0064] Then, a copper plated layer having average thickness of 15 μm wasformed on the nickel-zinc alloy layer 5 shaped into a circuit and on theinner wall of the via hole, thereby obtaining a printed-wiring board asshown in FIG. 7G. The copper plating was carried out by first catalyzingpalladium and forming a copper layer with thickness of 1 μm to 2 μm byelectroless copper plating, followed by carrying out electrolysis copperplating under conditions of current density of 15 A/dm² with a coppersulfate solution at a liquid temperature of 45° C. having concentrationsof sulfuric acid of 150 g/l and copper of 65 g/l.

[0065] The printed-wiring board 18 obtained as described above was usedto measure the peel strength at the interface between the outer circuit17 and the isolation layer 10. As a result, the dry peel strength was1.76 kgf/cm, and the level of UL heat resistance at rating 130° C.defined in the UL 796 Standard was 1.03 kgf/cm, both well surpassing thevalues (10 days) specifying the UL standard.

COMPARATIVE EXAMPLE 1

[0066] In this Comparative Example 1, the copper foil for printed-wiringboard 1 was produced in a method similar to that of Example 1 forproducing the printed-wiring board 18 in a similar way.

[0067] However, the composition of nickel and zinc in the nickel-zincalloy layer 5 was purposely deviated from the range according to thepresent invention in which the content of nickel is 70 to 88 wt % andthe content of zinc is the balance. Thus, for this nickel-zinc alloylayer 5, a pyrophosphate based solution was prepared using zincpyrophosphate (ZnP₂O₇.3H₂O), nickel sulfate (NiSO₄.7H₂O) and potassiumpyrophosphate (K₂P₄O₇) so that the solution had a composition with 1.0g/l of zinc, 1.5 g/l of nickel and 100 g/l of potassium pyrophosphate,and in the solution at a liquid temperature of 30° C., the copper foilitself was made to undergo cathode polaraization with the use of astainless plate for the counter electrode under conditions of currentdensity of 1 A/dm² and electrolysis time of 300 seconds, therebyproviding an alloy composition with 1.14 g/m² (59.1 wt %) of nickel and0.79 g/cm² (40.9 wt %) of zinc. The weight thickness of the nickel-zincalloy layer 5 was 1.93 g/m². In concurrence with this formation of thenickel-zinc alloy layer 5 on the nodular treatment side 4, 0.10 g/m² ofnickel-zinc layer was formed on the shiny side 6 of the untreated copperfoil 2 as a corrosion prevention layer.

[0068] Then, in the process of production of the printed-wiring board18, the untreated copper foil 2 on the both outer faces and the cuppercomponent of the copper microparticles 4 were first etched away forcarrying out laser drilling processing for the four-layer plate 11 shownin FIG. 2A, but when they were etched away, the nickel-zinc alloy layer5 having the above described composition was dissolved because thecontent of nickel in the nickel-zinc alloy layer 5 was low even if Aprocess solution (manufactured by Meltex Co., Ltd.) being so called analkali etchant was used as a etchant for copper, thus making itimpossible to conduct selective etching. As a result, the nickel-zincalloy layer 5 located on the both outer faces in FIG. 3B was removed,and therefore the printed-wiring board 18 could not be produced by amethod similar to that of Example 1.

COMPARATIVE EXAMPLE 2

[0069] In this Comparative Example 2, the copper foil for printed-wiringboard 1 was produced in a method similar to that of Example 1 to producethe printed-wiring board 18 in a similar way.

[0070] However, the composition of nickel and zinc in the nickel-zincalloy layer 5 was purposely deviated from the range according to thepresent invention in which the content of nickel is 70 to 88 wt % andthe content of zinc is the balance. Thus, for this nickel-zinc alloylayer 5, a pyrophosphate based solution was prepared using zincpyrophosphate (ZnP₂O₇.3H₂O), nickel sulfate (NiSO₄.7H₂O) and potassiumpyrophosphate (K₂P₄O₇) so that the solution had a composition with 0.6g/l of zinc, 10.0 g/l of nickel and 100 g/l of potassium pyrophosphate,and in the solution at a liquid temperature of 30° C., the copper foilitself was made to undergo cathode polaraization with the use of astainless plate for the counter electrode under conditions of currentdensity of 0.8 A/dm² and electrolysis time of 6000 seconds, therebyproviding an alloy composition with 7.74 g/m² (90.0 wt %) of nickel and0.86 g/cm² (10.0 wt %) of zinc. The weight thickness of the nickel-zincalloy layer 5 was 8.60 g/m². In concurrence with this formation of thenickel-zinc alloy layer 5 on the nodular treatment side 4, 0.02 g/m² ofnickel-zinc layer was formed on the shiny side 6 of the untreated copperfoil 2 as a corrosion prevention layer.

[0071] Then, in the process of production of the printed-wiring board18, the untreated copper foil 2 on the both outer faces and the cuppercomponent of the copper microparticles 4 were first etched away forcarrying out laser drilling processing for the four-layer plate 11 shownin FIG. 2A. When they were etched away. A process solution (manufacturedby Meltex Co., Ltd.) being so called an alkali etching solution was usedas an etchant for copper, whereby the nickel-zinc alloy layer 5 remainedwithout being dissolved, thus making it possible to leave thenickel-zinc alloy layer 5 exposed at the both outer faces as shown inFIG. 3B.

[0072] However, the content of zinc in the nickel-zinc alloy layer 5 waslow, and therefore as a result of measuring the peel strength at theinterface between the outer circuit 17 and the isolation layer 10, thedry peel strength was 1.92 kgf/cm, and the level of UL heat resistanceat rating 130° C. defined in the UL 796 Standard was 0.50 kgf/cm,showing that the printed-wiring board 18 had poor UL heat resistance.

COMPARATIVE EXAMPLE 3

[0073] In this Comparative Example, the step of producing theprinted-wiring board using a copper foil for printed-wiring boardcomprising only a nickel layer on the nodular treatment side of theelectrodeposited copper foil will be described. First, production of thecopper foil for printed-wiring board 1 will be described with referenceto the drawings. Here, an electrodeposited copper foil having a crosssection shown schematically in FIG. 8 for use in production of a copperfoil having nominal thickness of 18 μm, which had not been subjected tosurface treatment (hereinafter referred to as “untreated copper foil”)was used. Then, a so called surface treatment apparatus was used tosubject this untreated copper foil 2 to nodular treatment and surfacetreatment for forming the nickel layer.

[0074] In the surface treatment apparatus, copper microparticles 4 arefirst deposited on the surface of the matte side 3 of the untreatedcopper foil 2 under burnt copper plating conditions, and seal platingwas carried out as level copper plating conditions so as to prevent thecopper microparticles 4 from being dropped off, thereby depositingstably the copper microparticles 4 on the matte side 3 of the untreatedcopper foil 2. For the burnt copper plating conditions for the coppermicroparticles 4, plating was carried out under conditions of currentdensity of 30 A/dm² and electrolysis time of 4 seconds by using aninsoluble anode (DSE) for the counter electrode to make the copper foilitself undergo cathode polarization, in a copper sulfate solution at aliquid temperature of 30° C. with concentrations of copper and sulfuricacid being 12 g/l and 180 g/l, respectively. For the level copperplating conditions for the copper microparticles 4, plating was carriedout under conditions of current density of 15 A/dm² and electrolysistime of 4 seconds by using the insoluble anode (DSE) for the counterelectrode to make the copper foil itself undergo cathode polarization,in a copper sulfate solution at a liquid temperature of 30° C. withconcentrations of copper and sulfuric acid being 40 g/l and 180 g/l,respectively.

[0075] Then, a nickel layer 5 was formed on the surface with coppermicroparticles 4 provided thereon. For this nickel layer 5, a nickelsulfate based solution was prepared so that the solution had acomposition with 300 g/l of nickel sulfate (NiSO₄.7H₂O), 50 g/l ofnickel chloride (NiCl₂) and 40 g/l of boric acid (H₃BO₃), and in thesolution at a liquid temperature of 30° C., the copper foil itself wasmade to undergo cathode polaraization with the use of a stainless platefor the counter electrode under conditions of current density of 24A/dm² and electrolysis time of 12.6 seconds, thereby electro-depositing8.15 g/m² of nickel.

[0076] The reduced thickness of the nickel layer 5 is 0.92 μm. Inaddition, the surface with the nickel layer 5 formed thereon was treatedwith a silane coupling agent and then dried to produce the copper foilfor printed-wiring board 1 shown in FIG. 8. However, the silane couplingagent treated layer is not shown in the drawings.

[0077] Thereafter, the printed-wiring board 18 was produced by a methodsimilar to that used in Example 1, comprised of the steps shown in FIGS.2 to 5. This printed-wiring board 18 was used to measure the peelstrength at the interface between the outer circuit 17 and the isolationlayer 10. As a result, the dry peel strength was 1.85 kgf/cm, and thelevel of UL heat resistance at rating 130° C. defined in the UL 796Standard was 0.30 kgf/cm, apparently showing that the printed-wiringboard 18 had poor UL heat resistance.

[0078] Industrial Applicability

[0079] By using the copper foil for printed-wiring board according tothe present invention, laser drilling processing can easily be carriedout in the process of a printed-wiring board, and selective etchingadvantageous for formation of a fine pitch circuit can be conducted, andhigh UL heat resistance can be ensured for a conductor circuit finallyformed in the printed-wiring board. This copper foil for printed-wiringboard excellent in total balance, which is the first of its type, willmake it possible to introduce high quality printed-wiring boards to themarket.

1. A copper foil for printed-wiring board, said copper foil comprisingon one side a nodular treatment side to be bonded to a substrate,wherein the copper foil comprises on the nodular treatment side anickel-zinc alloy layer.
 2. The copper foil for printed-wiring boardaccording to claim 1, wherein the nickel-zinc alloy layer is constitutedby a nickel-zinc alloy having a composition with 70 wt % to 88 wt % ofnickel and the balance of zinc.
 3. The copper foil for printed-wiringboard according to claim 1 or 2, wherein the weight thickness of thenickel-zinc alloy layer is 0.7 g to 45 g per square meter of the nodulartreatment side of said copper foil.
 4. A copper foil for printed-wiringboard, said copper foil comprising on one side a nodular treatment sideto be bonded to a substrate, wherein a nickel layer is provided on thenodular treatment side, and a zinc layer or a zinc alloy layer isprovided on the nickel layer.
 5. The copper foil for printed-wiringboard according to claim 4, wherein the weight thickness (X) of thenickel layer is 0.7 g/m² to 45 g/m², and the weight thickness (Y) of thezinc layer is 0.01 g/m² to 2 g/m², and the equivalent thickness (T)calculated from Equation 1 is smaller than or equal to 5 μm.T=(X/8.85)+(Y/7.12)(μm)   [Equation 1]Specific gravity of nickel: 8.85g/m³ Specific gravity of zinc: 7.12 g/m³
 6. The copper foil forprinted-wiring board according to claim 4, wherein the weight thickness(X) of the nickel layer is 0.7 g/m² to 45 g/m², and the weight thickness(Y) of the zinc alloy layer containing n kinds of alloying elements is0.01 g/m² to 2 g/m², and the equivalent thickness (T) determined by thecalculation procedure shown in Equation 2 is smaller than or equal to 5μm. T=(X/8.85)+(Y/ρ _(sum))(μm)   [Equation 2][ρ_(sum) representsspecific gravity of the zinc alloy. This is a value converted asρ_(sum)={17.12×a+(ρ_(Me1)×b₁+ . . . +ρ_(Men)×b_(n)){/100, provided thatthe zinc alloy is comprised of a % by weight of Zn and n kinds ofalloying elements, each alloying element is represented by Me_(n), thecontent of the alloying element is b_(n)% by weight, and the specificgravity of the alloying element is ρ_(Men).]
 7. A copper clad laminateusing the copper foil for printed-wiring board according to claims 1 to6.